In bipolar diaphragm cells having interleaved anodes and cathodes, large electrolyte volumes are possible with small backplate areas. In such cells, large quantities of cathode gases, i.e., hydrogen, are evolved per unit area of backplate. The cathode gases contain entrained catholyte liquor, and when the cathode gases are recovered from the cell the catholyte liquor must be removed from the gas.
The presence of entrained catholyte liquor in the hydrogen causes foaming in the hydrogen gas outlet. This, in turn, inhibits hydrogen flow out of the catholyte chamber, causing slugging and surging of the catholyte liquor. The slugging and surging of the catholyte liquor is associated with oscillations in the hydrogen back pressure on the diaphragm, cathode current efficiency, and cell liquor strength. It is, therefore, advantageous to remove as much of the entrained cell liquor as possible prior to removing the hydrogen gas from the cell.